Cable-type drawbenches



March 26, 1968 s E 3,374,655

CABLE-TYPE DRAWBENCHES Filed Dec. 27, 1965 INVENTOR. FRED E. HALS'FEADATTORNEY United States Patent 3,374,655 CABLE-TYPE DRAWBENCHES Fred E.Halstead, Rochester, Pa., assignor to Halstead Metal Products, Inc.,Zelienople, Pa., a corporation of Pennsylvania Filed Dec. 27, 1965, Ser.No. 516,488 5 Claims. (Cl. 72-287) This invention relates to drawbenchesof the type employing cables for moving a draw carriage away from andtoward a stationary drawing die, and more particularly to improvementsin the take-up and adjustment of the cables of said drawbenches.

Cable-type drawbenches incorporate a cable system which consists of drawcables and return cables. The draw cables extend from the draw carriage,in the direction of draw, to a'prime mover which provides the powernecessary to draw the workpieces through the drawing die. The returncables extend from the draw carriage, in the opposite direction, to asecondary mover which, at the completion of a drawing operation, returnsthe draw carriage to a position adjacent the drawing die. The secondarymover may be incorporated into the prime mover or may comprise aseparate power component.

Cable-type drawbenches have several disadvantages which the presentinvention seeks to overcome. For example, long lengths of the cables insuch drawbenches, have an inherent catenary sag due to their weight.This is particularly true in the return cables when the draw carriage isdrawing workpieces through the drawing die. In the past, the catenarysag was eliminated, in part, by applying a very heavy preload to thecable system while the drawbench was idle. Some of the'preload remainedon the return cables during the drawing operation. However, even withthis heavy preload, a certain amount of sag and hence, slack, was alwayspresent in the return cables.

During a drawing operation, the draw cables are subjected to a largetensile force which tends to elongate them. The return cables, however,are under a very minor amount of tension, if any, inasmuch as thetensile forces in the draw cables are counterbalanced by the tensileforces in the workpieces being drawn. During the drawing operation, thereturn cables have a certain amount of sag or slack which does notatfect the drawing operation of the drawbench. However, at thecompletion of the drawing operation, the workpieces disengage from thedrawing die and the tensile forces in the workpieces are suddenlytransferred to the return cables. The draw carriage jumps forward, thatis, in the direction of draw, until such time as the tension on thereturn cables and the draw cables equalizes. There results a violentreaction which tends to snap the return cables as the full drawingtension in the draw cables is released and the draw cables suddenlyreturn to their normal shorter length. It should be evident that thisviolent reaction subjects the various drawbench components to severeshock loads which considerably shorten their operating life.

When the prime mover and secondary mover are combined and comprise asingle main hydraulic cylinder and piston assembly, it is conventionalto employ a cable reeving system comprising sheave devices arranged suchthat the short distance traveled by the piston is multiplied to move thedraw carriage over the full length of the track structure. In this andother cable-type drawbenches, it is necessary at installation andperiodically thereafter, to be able to adjust the position of the drawcarriage relative to the drawing die when the piston is at the end ofits stroke. This is necessary due to cable stretch. In the past, it hasbeen necessary to provide two take-up mechanisms, one at each end of thecable reeving system, for example.

ice

When an adjustment in the position of the draw carriage was necessary,one take-up mechanism was loosened and the other take-up mechanism wastightened until the required position of the draw carriage relative tothe drawing die was achieved. This manner of adjusting the position ofthe draw carriage is, of course, a time-consuming operation and requiresmany workmen for its completion.

Accordingly, as an overall object, the present invention seeks toprovide an improved cable-type drawbench which does not have theaforementioned disadvantages.

Another object of the invention is to provide improved take-up means forcable-type drawbenches whereby the sag or slack in the cables issubstantially entirely eliminated.

Still another object of the invention is to provide an improvedcabletype drawbench having cable slack take-up means whereby jumpingforward of the draw carriage and the subsequent whiplash action of thereturn cables are eliminated.

A further object of the invention is to provide a cabletype drawbenchwherein the position of the draw carriage relative to the drawing diemay be adjusted in a rapid manner with a minimum amount of labor.

The present invention is particularly useful in all of those drawbencheswherein cables connected between the draw carriage and a cableretracting mechanism, are used to return the draw carriage to itsstarting point adjacent the drawing die and wherein cables or othersuitable means are employed to forcibly move the draw carriage duringthe drawing operation.

The drawbench may employ a double-acting hydraulic cylinder, such asillustrated in the drawing, for forcibly moving the draw carriage orother types of drive means, such as electric motors.

In accordance with the present invention, means is provided for applyinga preselected tensile force on the return cables, of an amountsuflicient to eliminate substantially entirely all sage in the returncables. The tensile force applying means is operated at all times duringoperation of the drawbench, that is, during the draw stroke, during thereturn stroke and during the idle time required to introduce newworkpieces through the drawing die and into the gripper jaws of the drawcarriage.

The tensile force applying means preferably comprises a single-actinghydraulic operated piston and cylinder means wherein the piston isconnected to the return cables. Conduit means connected to the cylinder,introduces pressurized operating fluid therein which, acting on thepiston and cylinder, creates the aforesaid preselected tensile force inthe return cables. Control elements are provided in the conduit meansfor (a) maintaining the working fluid at a preselected pressure levelsufiicient to produce the aforesaid preselected tensile force, and (b)for relieving, at a moderate rate, those excessive pressures created inthe piston and cylinder means when the large tensile forces in theworkpieces being drawn are suddenly transferred to the return cables asthe workpieces disengage from the drawing die.

Further, in accordance with the invention, a single cable adjustmentmeans is provided for adjusting the position of the draw carriagerelative to the drawing die. The tensile force applying means isarranged such that the position of the draw carriage may be adjustedwhile the tensile force applying means is operating.

The above and other objects and advantages of the present invention willbecome apparent from the following detailed description by reference tothe accompanying drawing, in which there is illustrated a cable-typedrawbench incorporating the improved cable take-up and adjustment meansof the invention.

General description or guideways 26; a hydraulic actuating cylinder 28secured to a stationary support member 30; a pair of distancemultiplying cable and sheave assemblies 32, 34 disposed at the draw andreturn ends, respectively, of the drawbench a reversible, variablevolume, high pressure pump 36 connected to the hydraulically actuatedcylinder 28 by means of conduits 38, 40; and a constant speed, electricmotor 42 for driving the pump 36. In accordance with the invention, thedrawbench 10 further includes a tensile force applying means 44 actingon the return cable of the distance multiplying cable and sheaveassembly 34, and a single cable adjustment means 46 acting on the drawcable of the distance multiplying cable and sheave assembly 32.

As is known, the draw carriage 16 is guided by the track structure 22 inits movement away from the die 12 during the draw stroke and toward thedie 12 during the return stroke. During the draw stroke, workpiecesrepresented herein by the dash-dot centerlines 48, are

clamped by the gripper jaws 18 of the draw carriage 16' and are pulledthrough the die openings 14 of the drawing die 12.

The hydraulic actuating cylinder 28 comprises a cylinder 50 having apiston 52 which is slideable longitudinally through the cylinder 50. Afirst piston rod 54 is secured to the piston 52 and extends away fromthe drawing die 12 toward the distance multiplying cable and sheaveassembly 32. A second piston rod 56 is secured to the piston 52 andextends toward the drawing die 12 and the dis tance multiplying cableand sheave assembly 34. The piston 52 has a first piston face 58adjacent the first piston rod 52 and a second piston face 60 adjacentthe second piston rod 56. The diameter of the first piston rod 54 isless than the diameter of the second piston rod 56. Consequently, thearea of the first piston face 58 is greater than the area of the secondpiston face 60. The overall arrangement is such that the force createdwhen working fluid acts on the first piston face 58 will be considerablygreater than the force created when working fluid acts on the secondpiston face 60. During the drawing stroke, working fluid is communicatedinto the cylinder 50, by means of the conduit 38 to act on the firstpiston face 58 and thereby provide the large force required to draw theworkpieces 48 through the drawing die 12. Conversely, during the returnstroke working fluid is introduced into the cylinder 50, by way of theconduit 40, to act on the second piston face 60 and thereby provide thelesser force required to return the draw carriage 16 to its startingposition adjacent the drawing die 12.

The distance multiplying cable and sheave assemblies 32, 34 provide adistance multiplication of 4:1. That is to say, the draw carriage 16will be moved four feet for each foot of travel of the piston 52. Thedistance multiplying cable and sheave assemblies 32, 34 aresubstantially identical and comprise, in general, first stationary 7 orfixed sheave carriages 62, 64, the carriage 62 being positioned at thatend of the track structure 22 remote from the die 12 and the carriage 64being positioned adjacent to the die 12; second stationary or fixedsheave carriages 66, 68 being positioned adjacent to the first sheavecarriages 62, 64, respectively; movable sheave carriages 70, 72, themovable carriage 70 being secured to the end of the first piston rod 54and the movable carriage 72 being secured to the end of the secondpiston rod 56; intermediate sheave devices 74, 76 adjacent thestationary sheave carriages 62, 64, respectively; a draw cable 78; and areturn cable 80.

devices 82 of the stationary carriage 62, toward and around sheavedevices 84 carried on the movable carriage 70, toward and around sheavedevices 86 carried on the second stationary sheave carriage 66, towardand around sheave devices 88 on the movable sheave carriage 70, andfinally toward and around the intermediate sheave device 74. With thisarrangement, a single predetermined length of cable is employed.

In a similar fashion, the return cable is connected to the draw carriage16 and extends therefrom in a direction opposite to the direction ofdraw about sheave devices 90 of the first stationary sheave carriage 64,toward and around sheave devices 92 carried by the movable sheave device72, toward and around sheave devices 94' carried by the secondstationary sheave carriage 68, toward and around sheave devices 96carried by the movable sheave carriage 72, and finally, toward andaround the intermediate sheave device 76.

It should be evident, that as the piston 52 is moved toward the drawingdie 12, the upper reach of the draw cable 78, that is, that portionextending from the draw carriage 16, will be retracted so that thedrawcarriage 16 is moved away from the drawing die 12. Conversely,

when the piston 52 moves away from the drawing die 12, the upper reachof the return cable 80 will be retracted so that the draw carriage 16 ismoved toward the drawing die 12.

The above-mentioned distance multiplication is, of

course, obtained by the arrangement of the various sheave" 6 devices.Inasmuch as four strands of the draw cable 78, for example, extendbetween the stationary sheave carriages 62, 66 and the movable sheavecarriage 70, the mechanical advantage has a value of four. Consequently,the carriage 16 will be moved four feet for each foot traveled by thepiston 5'2.

Tensile force applying means 44 The tensile force applying means 44, ofthe invention, preferably comprises a single-acting hydraulic. cylinder98 having a piston 100'which is slideable longitudinally therein. Apiston rod 102 has one of its ends connected to the piston 100 and theother of its ends connected to a;

may comprise a part of a main sump 112 from which the pump 36 drawsworking fluid.

In the conduit 106 there is provided a check valve 114 and a pressurereducing valve 116 which is positioned downstream of the check valve114. The pressure reducing valve 116 is of the self-bleeding type havinga bleed conduit 118 extending to the main sump 112. As will be describedin greater detail, working fluid will be returned to the main sump 112by way of the bleed conduit 118 when the pressure in the hydrauliccylinder 98 exceeds a predetermined pressure level.

Cable adjustment means 46 In accordance with the present invention andas stated above, a single cable adjustment means 46 is provided whichacts on the draw cable 78. The cable adjustment means 46 may comprise,for example, a rod 120 having one of its ends connected to a clevismember 122 which supports the intermediate sheave device 74 and havingits opposite end threaded and extending through a support block 124 anda nut 126. Rotation of the nut 126 in one direction will cause the rod120 and hence the intermediate sheave device 74 to be moved toward thedie block 12 while rotation of the nut '126 in the opposite directionwill cause the rod 120 and hence the intermediate sheave device 74 to bemoved away from the drawing die 12. It should be noted at this time thatany other suitable cable adjustment means may be employed.

Operation of tensile force applying means 44 The function of the tensileforce applying means 44 is to place the return cable 80 under suflicienttension such that substantially entirely all sag or slack is eliminatedfrom the return cable 80. As will now be explained, certain advantagesresult from tensioning the return cable 80.

During the draw stroke, the pump 36 pressurizes the working fluid andconveys the same through the conduit 38 to the main hydraulic cylinder28. Pressurized working fluid is also conveyed to the cylinder 98 by wayof the conduit 106. However, the pressure of the working fluid isreduced by the pressure reducing valve 116, to a preselected pressurelevel which is suflicient to produce the aforesaid preselected tensileforce in the return cable 80.

At the start of the draw stroke, the piston 52 moves toward the drawingdie 12. The draw cable 78 will undergo a certain amount of elongationuntil the force required to draw the workpieces 48 through the die 12has been attained. Consequently, as the draw cable 78 is elongated, thetension in the return cable 80 tends to be reduced and, in the absenceof the hydraulic cylinder 98, would result in sag or slack in the returncable 80'. However, the hydraulic cylinder 98 maintains the return cable80 under sufiicient tension whereby substantially entirely all sag orslack is eliminated. The return cable 80 will also be elongated slightlyby the applied tensile force.

At the completion of the draw stroke, the workpieces 48 disengagethemselves from the drawing die 12 and the tensile forces which were inthe workpieces 48 are suddenly transferred to the return cable 80. Atthis time, the draw cable 78 attempts to return to its shorter length bytending to pull the draw carriage 16 and the return cable 80 in thedirection of draw. The tensile forces in the draw cable 78 will bereduced until they are equal to and opposed by the tensile forces in thereturn cable 80. Since the return cable 80 is itself under tension andhas substantially no sag or slack, the draw carriage 16 and the returncable 80 will move only a very slight distance in the direction of draw.Consequently, the drawbench components are not subjected to the shockloads which would result if there was sag or slack in the return cable80.

As the draw cable 78 contracts and tightens, the pressure in thehydraulic cylinder 98 is intensified, that is, increased above thepreselected pressure level. The pressure reducing valve 116 willgradually bleed excess working fluid to the bleed conduit 118 until suchtime as the excessive pressure within the cylinder 98 are relieved andthe pressure within the cylinder 98 returns to the aforesaid preselectedpressure level. Hence, the excessive backpressures created in thehydraulic cylinder when the workpieces are disengaged from the drawingdie, are relieved at a rate which prevents damage to the variousdrawbench components.

As is known, differences in the metallurgy and the physical propertiesof the workpieces 48 may cause one or more of the workpieces 48 to bedisengaged from the drawing die 12 before the remaining workpieces 48are disengaged, that is, the workpieces 48 are not simultaneouslydisengaged from the drawing die 12. In this instance, the tensile forcesin the workpieces 48 will be transferred to the return cable 80 in astepwise manner. In turn, the hydraulic cylinder 98 and the pressurereducing valve 116 will cooperate and operate as described above, toreduce the resulting excessive backpressures in a stepwise manner.

6. Operation 0] cable adjustment means 46 The function of the cableadjustment means 46 is to reposition the draw carriage 16 relative tothe drawing die 12. More specifically, when the piston 52 of the mainhydraulic cylinder 28 is at the end of its stroke, that is, adjacent theconduit 38, the draw carriage 16 is at its starting position adjacent tothe drawing die 12. Because of:variations in cable stretch, the drawcarriage 16 will not, at all times, return to the exact startingposition, as required. Consequently, at installation and periodicallythereafter, the position of the draw carriage 16 must be adjustedtocorrespond to the desired starting position.

In the drawbench 10, only a single cable adjustment means 46 is includedand required to reposition the draw carriage 16 relative to the die 12.In prior art drawbenches, two cable adjustment means were required, oneacting on the draw cable. and the other acting on the return cable.

When it becomes necessary to reposition the draw carriage 16, the nut126 is rotated in the direction which will move the draw carriage 16either away from the die 12 or toward the die 12 so. that the drawcarriage 16 is moved to the desired starting location. In the case wherethe draw carriage 16 must be moved toward the drawing die 12, the nut126 must be rotated in a clockwise direction, assuming right-handthreads, such that the draw cable 78 is loosened. At this time, theworking fluid acting on the piston will draw the return cable 80 to takeup the slack in the draw cable 78. This process is continued until thedraw carriage 16 is positioned at the exact desired starting position.

In the case where the draw carriage must be moved away from the drawingdie 12, the nut 126 is rotated in a counterclockwise direction so thatthe tension in the draw cable 78 and the return cable 80 is increased.The increased cable tension will, of course, intensify the pressurewithin the hydraulic cylinder 98. The excessive pressure is, asdescribed above, relieved by the pressure reducing valve 116 by bleedingworking fluid to the bleed conduit 118. This process is continued untilsuch time as the draw carriage 16 is moved to the exact requiredstarting position.

Alternative arrangement As stated above, the present tensile forceapplying means 44 and the take-up adjustment means 46 are applicable toany drawbench having a return cable which, in the absence of thesemeans, would sag during the drawing operation. In those drawbencheswherein prime movers other than the main hydraulic cylinder is employed,a small auxiliary power unit may be provided. Such an auxiliary pumpingunit is illustrated in the drawing in dash-dot outline as comprising,for example, a small auxiliary pump 130 driven by an electric motor 132and having a sump 134 associated therewith. The auxiliary pump 130 wouldpressure working fluid and convey the same to the conduit 106 to thehydraulic cylinder 98. The bleed line 118 would, of course, extend tothe sump 134.

Although the invention has been shown in connection with certainspecific embodiments, it will be readily apparent to those skilled inthe art that various changes in form and arrangement of parts may bemade to suit requirements without departing from the spirit and scope ofthe invention.

I claim as my invention:

1. In a drawbench having a drawing die, a track structure extendingparallel to the central axis of said drawing die, a draw carriagemovable along said track structure for pulling workpieces through saiddrawing die, return cable means connected to said draw carriage andextending therefrom in a direction opposite to the direction of draw,and means operable on said return cable means for returning said drawcarriage adjacent said drawing die, the improvement comprising: meansincluding a hydraulic cylinder for applying a preselected tensile forceon said return cable means in a direction opposite to the direction ofdraw and of an amount sufi'icient to eliminate substantially entirelyall sag in said return cable means.

2. The improvement as defined in claim 1 including valve means formaintaining the pressure of operating fluid in said hydraulic cylinderat a preselected pressure level sufficient to create said preselectedtensile force, and means for relieving excessive backpressures createdin said hydraulic cylinder when the workpieces disengage from saiddrawing die.

3. The improvement as defined in claim 1 including valve means formaintaining the pressure of operating fluid in said hydraulic cylinderat a preselected pressure level suflicient to create said preselectedtensile force and bleed means incorporated into said valve means forbleeding a quantity of the working fluid from said hydraulic cylinder torelieve excessive backpressures created in said hydraulic cylinder whenthe workpieces disengage from said drawing die.

4. The improvement as defined in claim 1 including single means at thedraw end of said track structure for moving said draw carriage towardand away from said 8 drawing die to adjust the position of said drawcarriage relative to said drawing die.

5. The improvement as defined in claim 1 including single means at thedraw end of said track structure for moving said draw carriage alongsaid track structure to adjust its position relative to said drawingdie, valve means for introducing operating fluid into said hydrauliccylinder to raise the pressure of operating fluid to said preselectedpressure level when said draw carriage is moved toward said drawing dieby said adjustment means, and means for relieving excessivebackpressures in said hydraulic cylinder above said preselected pressurelevel when said draw carriage is moved away from said drawing die bysaid adjustment means.

References Cited UNITED STATES PATENTS 1,475,701 11/1923 John 72-291 YCHARLES w. LANHAM, Primary Examiner.

H. D. HO'INKES, Assistant Examiner.

1. IN A DRAWBENCH HAVING A DRAWING DIE, A TRACK STRUCTURE EXTENDINGPARALLEL TO THE CENTRAL AXIS OF SAID DRAWING DIE, A DRAW CARRIAGEMOVABLE ALONG AND SAID TRACK STRUCTURE FOR PULLING WORKPIECES THROUGHSAID DRAWING DIE, RETURN CABLE MEANS CONNECTED TO SAID DRAW CARRIAGE ANDEXTENDING THEREFROM IN A DIRECTION OPPOSITE TO THE DIRECTION OF DRAW,AND MEANS OPERABLE ON SAID RETURN CABLE MEANS FOR RETURNING SAID DRAWCARRIAGE ADJACENT SAID DRAWING DIE, THE IMPROVEMENT COMPRISING: MEANSINCLUDING A HYDRAULIC CYLINDER FOR APPLYING A PRESELECTED TENSILE FORCEON SAID RETURN CABLE MEANS IN A DIRECTION OPPOSITE TO THE DIRECTION OFDRAW AND OF AN AMOUNT SUFFICIEN TTO ELIMINATE SUBSTANTIALLY ENTIRELY ALLSAG IN SAID RETURN CABLE MEANS.